For babies born early, corrected (adjusted) age tells you how old they would be if born on their due date. Enter the birth date and either the original due date or weeks of pregnancy at birth to see both chronological and corrected age, plus when each corrected milestone falls.
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I know the
weeks
days
Enter your values to see the result.
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How to use the Corrected Age Calculator
Enter the date of birth and the date you want the age for.
Choose what you know: weeks of pregnancy at birth or the original due date.
Enter the weeks and days (for example 32 + 3) or the due date.
Read the corrected age next to the chronological age.
Use the table to see when your baby reaches each corrected milestone.
Corrected age formula
Weeks early = 40 − gestational age at birth (weeks)
Corrected age = chronological age − weeks early (which is the same as age counted from the due date)
Example: a baby born at 32 weeks + 0 days is 8 weeks early. At 5 months old (about 21.7 weeks), the corrected age is about 13.7 weeks, roughly 3 months.
Corrected age quick reference
Born at
Weeks early
Corrected age at 3 months
at 6 months
at 12 months
26 weeks
14
not yet (≈ 1 week before due date)
≈ 2.8 months
≈ 8.8 months
28 weeks
12
≈ 0.2 months
≈ 3.2 months
≈ 9.2 months
30 weeks
10
≈ 0.7 months
≈ 3.7 months
≈ 9.7 months
32 weeks
8
≈ 1.2 months
≈ 4.2 months
≈ 10.2 months
34 weeks
6
≈ 1.6 months
≈ 4.6 months
≈ 10.6 months
36 weeks
4
≈ 2.1 months
≈ 5.1 months
≈ 11.1 months
Months here are average months (4.35 weeks). Preterm categories: extremely preterm under 28 weeks, very preterm 28–31, moderately preterm 32–33 and late preterm 34–36 weeks.
Frequently asked questions
What is corrected age?
Corrected age (also called adjusted age) is a premature baby's age counted from their due date instead of their birth date. It equals chronological age minus the number of weeks the baby was born early.
How do I calculate corrected age?
Subtract the weeks born early from the actual age. A baby born at 30 weeks was 10 weeks early (40 − 30). At 6 months old (about 26 weeks), corrected age is 26 − 10 = 16 weeks, or about 4 months.
Why is corrected age used?
Development depends on time since conception, not time since birth. Doctors use corrected age to judge milestones like rolling, sitting and talking, and to plot growth for preterm babies, so a baby born early isn't compared with term babies who had extra weeks in the womb.
When do you stop using corrected age?
Most doctors stop correcting at about 2 years of chronological age, when most preterm babies have caught up. For very premature babies some specialists continue a little longer.
Should vaccines follow corrected age?
No. Vaccines are given by chronological age (time since birth), even for premature babies, unless your doctor says otherwise. Corrected age is used for development and growth.
What is postmenstrual age?
Postmenstrual age is gestational age at birth plus chronological age. It is used in the neonatal unit before the due date: a baby born at 30 weeks who is 4 weeks old has a postmenstrual age of 34 weeks.
Which babies need corrected age?
Babies born before 37 completed weeks of pregnancy (preterm). For babies born at 37 weeks or later, corrected and chronological age are treated as the same.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.